SafeFile: do endian-swap on float tag values

There are comments noting that writing raw float values may not be
endian-correct and indeed it is not.  WX does not provide functions for
endian-swapping floats, but since amule explicitly uses exclusively
single-precision (32-bit) floats, just cast it into a uint32_t for the
swapping.

This is a no-op on little-endian.

src/SafeFile.cpp

@@ -31,6 +31,7 @@
 #include <common/Format.h>		// Needed for CFormat
 #include "CompilerSpecific.h"		// Needed for __FUNCTION__
 
+#include <cstring>              // For std::memcpy
 
 #define CHECK_BOM(size, x) ((size >= 3)  && (x[0] == (char)0xEF) && (x[1] == (char)0xBB) && (x[2] == (char)0xBF))
 
@@ -189,7 +190,11 @@ float CFileDataIO::ReadFloat() const
 {
 	float retVal;
 	Read(&retVal, sizeof(float));
-	return retVal;
+    uint32_t toswap{};
+    std::memcpy(&toswap, &retVal, sizeof(toswap));
+    toswap = ENDIAN_SWAP_32(toswap);
+    std::memcpy(&retVal, &toswap, sizeof(retVal));
+    return retVal;
 }
 
 
@@ -306,6 +311,10 @@ void CFileDataIO::WriteHash(const CMD4Hash& value)
 
 void CFileDataIO::WriteFloat(float value)
 {
+    uint32_t toswap{};
+    std::memcpy(&toswap, &value, sizeof(toswap));
+    toswap = ENDIAN_SWAP_32(toswap);
+    std::memcpy(&value, &toswap, sizeof(value));
 	Write(&value, sizeof(float));
 }